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AIXpert Blog

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AIXpert Blog is about the AIX operating system from IBM running on POWER based machines called Power Systems and software related to it like IBM Systems Director, PowerVM for virtualisation and PowerSC for security plus performance monitoring and nmon

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Update in 2016: Please note this blog is from 2011 during the initial POWER7 days and technology has moved on with faster CPUs and memory in addition there has been software improvements. I am amazed how many good computer people read this and assume this blog is true to all time! Virtual Ethernet is faster now but there is also a warning here. Here is an analogy. Most vehicles can do 10 MPH (including me on a bike), most cars can do 100 MPH (including my family car) but very few vehicles can do 1000 MPH. That last times ten multiplier is... [More]

This mysterious AIX CPU Folding area is often misunderstood, so below is what I know from osmosis from talking to various guru level developers over the last 10 years. Shared Processor virtual machines (LPARs for the old fashioned) have a setting called Virtual Processors (or VP for short). This is the number of physical CPUs that the virtual machines can spread out across - in fact, I prefer to call it the "spreading factor" as it is much more obvious what it means. This can be the upper threshold for the number of CPUs that can be... [More]

I am not making a claim to fame (OK, I am really) but the UK Power Systems Advanced Technical Support group (that is me and Gareth) dropped the term "LPAR" or Logical Partition as a New Years resolution. We like to occasionally test to see if we can influence other IBMers and the IT Industry. We now in 2011 onwards use the terms: Virtual Server - this is the term used by Systems Director for over three years. While I can live with that name but the abbreviation of VS - it just does not feel or sound right. Virtual Machine - this... [More]

This is a follow on to a previous blog on " PowerVM Virtual Ethernet Speed is often confused with VIOS, SEA IVE/HEA speed "- here is a Direct Link I regularly get asked : "I have just heard about this [PowerVM virtual switch | vSwitch | Hypervisor Ethernet Switch] is available but I can't find out any information at all, help!" They are wanting to run two (or more) virtual switches within the one Power machine to completely separate the network packets of groups of virtual machines (LPARs) so they know for sure there can... [More]

I often get asked: How large to make a pair of Virtual I/O Server (VIOS)? The classic consultant answer is "it depends on what you are doing with Disk & Network I/O" is not very useful to the practical guy that has to size a machine including the VIOS nor the person defining the VIOS partition to install it! Added new guidance at the bottom in RED Observations : The VIOS server unfairly gets a bad press but note: Physical adapters are now in the VIOS, so device driver CPU cycles (normally hidden and roughly half of the OS CPU... [More]

The title should read "Local, Near & Far ..." - I will not correct it or links might fail. In this entry we carry on from part 5 but we are going to look at setting the virtual processor number for the virtual machine . There is a side effect that is not obvious and after 6 years of using them, it never occurred to me so perhaps it is news to others too. The problem of virtual processors is that they are ephemeral - i.e. they don't actually exist and costs nothing. So I find most systems administrators feel they can be generous... [More]

N-Port Id Virtualisation (NPIV) and virtual Fibre Channel adapters - like high speed physical adapters (see an earlier blog) do require memory to operator at full speed. NPIV effectively turns the Virtual I/O Server (VIOS) into a kind of virtual SAN switch where packets are passed through with no changes from the physical adapter to the client Virtual Machine (LPAR). I found it very hard to find a recommendation in the documentation but was given a rule of thumb. As before it should be noted that starving the VIOS and the Hypervisor of... [More]

I thought I should summarise the long eleven part Local, Near & Far POWER7 Affinity series. 1) Placement: Find out the layout of your boxes CPU and RAM and if the RAM is evenly distributed across available DIMMs Find out the placement of your Virtual Machines (LPARs) with lssrad -av - or - topas -M 2) SMT4 : Expect POWER7 SMT4 CPU use to “look” different POWER5 & 6 have two equal threads POWER7 shuts down threads 3 & 4 and even thread 2 - when there is not enough processes running. 3) Entitlement : Only set minimum Entitlements,... [More]

After you have started and used your virtual machine (VM) for a while, you may decide to change its size using a Dynamic LPAR (DLPAR) change from the HMC (or SDMC or IVM, of course). This has virtual machine placement implications. When shrinking your VM, the hypervisor will decide which CPU or memory (LBM) to release and it might not select what you think is the obvious choice. When enlarging your VM, we might thing there is an obvious way to grow in a balanced way but we can't see: 1) where physically our virtual machine is placed in the... [More]

I get email a few times a week like "Nigel, what do you recommend for getting a good view of what the whole Power Server is doing, what resources are free for reuse for further Virtual Machines and which Virtual Machines are busy" My detailed thoughts are on the DeveloperWorks AIX wiki here: AIX Other Performance Tools but it appears no one reads websites any more, so I thought I would blog a few examples by screen capture to illuminate what is available. My first Whole Power Server and Virtual Server view recommendation is Systems... [More]

Another good questions from a customer and my answer was simple: The PowerVM internal network on POWER machines operates just like a physical network. If two LPAR are on the same internal network and the root user puts the virtual adapter in to promiscuous mode then it can see all packets. Just like a physical network. If the two LPARs are on different internal networks then they can never see the other LPARs packets. Just like two physical networks. If two LPAR are on the same internal network but on different VLANs then they can never see... [More]

I have been touring cities in Europe: Birmingham for the 4 day Technical University, Manchester, central London and Dublin for the Ask the Experts 1 day event and last week Copenhagen for a POWER & AIX User group Technical Event. I have had about 250 to 300 people in my sessions and asked every time - How knows about the AIX Virtual User Group and only had about 30 people put their hands up. I am amazed how few people have found this invaluable resource. The organiser, Joe Armstrong an IBMer, set-ups up roughly monthly world wide... [More]

We all tend to concentrate on the CPU first and the memory second. CPUs, as the "brains" of the machine, does get a high focus and have a lot of extreme technology within it but the RAM is the "guts" of the machine to "feed" the CPU with nutrient data. OK, let us stop the analogy there :-) Along with reducing the number of CPUs via a lower virtual processor count, we also need to have the CPUs matching the memory - so AIX has a fighting change to localise a running process to its home SRAD and thus have it's data... [More]

The title should read "Local, Near & Far ..." - I will not correct it or links might fail. With a shared processor virtual machine (I am calling this "VM" but was called LPAR!) there are various suggestions of setting Entitlement ("Desired processing units" on the LPAR profile on the HMC, I am calling this "E") and Virtual Processor numbers (I am calling this "VP"). For Capped, the Entitlement is the maximum guaranteed CPU time that you can't go over and you round up the Entitlement to the... [More]

While I was installing a re-purposed POWER6 machine over the weekend, got round to installing my Dual Virtual I/O Servers, from DVD and then upgrading from there and I noticed a new service pack 2 for the latest VIOS version. It must have sneaked out without me noticing and there is a Interim fix too. The VIOS 2.2.0.12-FP24 SP2 Readme highlights lots of fixes including some for the Shared Storage Pool feature. A feature that I have been using and talking about (see this blog for more information). This got me thinking! I talk to lots... [More]